Gas and liquid phase catalytic Beckmann rearrangement of oximes to produce lactams

ABSTRACT

Methods for producing lactams from oximes by performing a Beckmann rearrangement using a silicoaluminophosphate catalyst are provided. These catalysts may be used in gas phase or liquid phase reactions to convert oximes into lactams. High conversion of oxime and high selectivity for the desired lactams are produced using the disclosed methods, including high conversion and selectivity for ε-caprolactam produced from cyclohexanone oxime and high conversion and selectivity for ω-laurolactam produced from cyclododecanone oxime.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/658,495 Oct. 23, 2012, which claims the benefit under 35U.S.C. §119(e) of U.S. Provisional Patent Application Ser. No.61/628,419 filed Oct. 28, 2011, the disclosures of which are herebyincorporated by reference in their entirety.

FIELD

The present invention relates to methods of producing lactams, such ascaprolactam, for example. In particular, the present invention relatesto a method producing caprolactam utilizing silicoaluminophosphate(SAPO) catalysts.

BACKGROUND

Traditional approaches for producing lactams, used in the production ofnylon, include an oxime undergoing a Beckmann rearrangement in thepresence of an acid catalyst such as fuming sulfuric acid. Exemplaryreactions are shown in FIG. 1. As illustrated in FIG. 1A, cyclohexanoneoxime is reacted to form ε-caprolactam, ε-caprolactam in turn ispolymerized to form Nylon-8. As illustrated in FIG. 1B, cyclododecanoneoxime is reacted to form ω-laurolactam, ω-laurolactam in turn ispolymerized to form Nylon-12. Nylon-8 and nylon-12 are extensively usedin industry and manufacturing.

One potential reaction mechanism for the reaction of FIG. 1A isillustrated in FIG. 1C. The mechanism generally consists of protonatingthe hydroxyl group, performing an alkyl migration while expelling thehydroxyl to form a nitirium ion, followed by hydrolysis,tautomerization, and deprotonation to form the lactam.

Typically, Beckmann rearrangement reactions of oximes to form lactamsare performed using acids such as fuming sulfuric acid. These reactionsare characterized by complete or nearly complete conversion of the oximeand very high selectivity for the desired lactams. However, thesereactions also produce byproducts including ammonium sulfate. Althoughammonium sulfate is a useful product in itself, minimizing itsproduction may be desirable.

Gas-phase and liquid-phase Beckmann rearrangement of cyclohexanoneoximes are known, which employ various natural and synthetic catalystsincluding solid-acid catalysts. However, the reported results providelow conversion of the oxime and low selectivity of the desired lactamproducts.

Improvements in the foregoing processes are desired.

SUMMARY

The present disclosure provides methods for producing lactams fromoximes by performing a Beckmann rearrangement using asilicoaluminophosphate catalyst. These catalysts are used in gas phaseor liquid phase reactions to convert oximes into lactams. Highconversion of oxime and high selectivity for the desired lactams areproduced using the disclosed methods, including high conversion andselectivity for ε-caprolactam produced from cyclohexanone oxime and highconversion and selectivity for ω-laurolectam produced fromcyclododecanone oxime.

In one exemplary embodiment, the present invention provides a method ofperforming a Beckmann rearrangement reaction. The method comprisesreacting an oxime in a liquid phase in the presence of a catalyst toproduce a lactam, said catalyst comprising a silicon-containingaluminophosphate with the IZA framework code FAU.

In another exemplary embodiment, the present invention provides anothermethod of performing a Beckmann rearrangement reaction. The methodcomprises reacting an oxime in a gas phase in the presence of a catalystto produce a lactam, said catalyst comprising a silicon-containingaluminophosphares with the IZA framework code FAU; wherein said reactingstep further comprises the combination of conversion of oxime andselectivity of the lactam is selected from the group consisting of; theconversion of the oxime is at least 50% and the selectivity of thelactam is at least 90%; and the conversion of the oxime is at least 90%and the selectivity of the lactam is at least 80%.

In still another exemplary embodiment, the present invention provides acatalyst. The catalyst comprises, a silicon-containing aluminophosphateframework with the IZA framework code FAU; and a plurality of discreteBrønsted acid sites positioned in an interior of the framework, the acidsites comprising silicon isomorphously substituted for phosphorous inthe framework; wherein the catalyst is a SAPO-37 type catalyst, and atleast 10% of the total number of acid sites are characterized as weakacid sites.

In still another exemplary embodiment, a method of performing a Beckmannrearrangement reaction is provided. The method comprises reacting anoxime in a liquid or gas phase in the presence of a catalyst to producea lactam, said catalyst comprising a silicon-containing aluminophosphatewith the IZA framework code FAU; wherein where the oxime is in a gasphase said reacting step further comprises the combination of conversionof oxime and selectivity of the lactam is selected from the groupconsisting of: the conversion of the oxime is at least 50% and theselectivity of the lactam is at least 90%; and the conversion of theoxime is at least 90% and the selectivity of the lactam is at least 80%.

The above mentioned and other features of the invention, and the mannerof attaining them, will become more apparent and the invention itselfwill be better understood by reference to the following description ofembodiments of the invention taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates the reaction from cyclohexanone oxime toε-caprolactam;

FIG. 1B illustrates the reaction from cyclododecanone oxime toω-laurolactam;

FIG. 1C illustrates the potential steps of a reaction corresponding to aBeckmann rearrangement reaction from cyclohexanone oxime toε-caprolactam;

FIGS. 2A-2G illustrate a structures of an exemplary SAPO-37 catalyst;

FIG. 3A is a ternary diagram showing the compositional parameters of oneembodiment of the silicoaluminophosphates in terms of mole fractions ofsilicon, aluminum, and phosphorous;

FIG. 3B is a ternary diagram showing the compositional parameters offurther embodiments of the silicoaluminophosphates in terms of molefractions of silicon, aluminum, and phosphorous;

FIGS. 4A-4C correspond to Example 2, and illustrate results from ²⁹SiSolid state NMR characterization of SAPO-37 catalysts;

FIG. 5 corresponds to Example 2, and illustrates, results fromNH₃-Temperature Programmed Desorption characterization of SAPO-37catalysts;

FIG. 8 corresponds to Example 2, and illustrates results from X-RayDiffraction characterization of SAPO catalysts;

FIG. 7 corresponds to Example 2; and illustrates results from BETsurface area characterization of SAPO-37 catalysts;

FIGS. 8A-8C correspond to Example 2, and are SEM pictures of SAPO-37catalysts;

FIGS. 9-15 correspond to Example 3, and illustrate the conversion andselectivity results of gas phase Beckmann rearrangement reactions ofcyclohexanone oxime to ε-caprolactam using various catalysts;

FIGS. 16-20 correspond to Example 4, and illustrate the conversion andselectivity results of liquid phase Beckmann rearrangement reactions ofcyclohexanone oxime to ε-caprolactam using various catalysts; and

FIGS. 21 and 22 correspond to Example 5, and illustrate the conversionand selectivity results of liquid phase Beckmann rearrangement,reactions of cyclododecanone oxime to ω-laurolactam using variouscatalysts.

DETAILED DESCRIPTION

The present disclosure is directed to a method to form lactams fromcyclic oxime compounds. Exemplary reactions are shown in FIG. 1. Asillustrated in FIG. 1A, cyclohexanone oxime is reacted to formε-caprolaetam, which in turn can be polymerized to form Nylon-8. Asillustrated in FIG. 1B, cyclododecanone oxime is reacted to formω-laurolactam, which in turn can be polymerized to form Nylon-12. Inother exemplary embodiments, additional lactams besides ε-caprolactamand ω-laurolactam are produced from corresponding oximes via thismethod. The present method is also useful to perform other Beckmannrearrangement reactions.

The methods according to the present disclosure include an oximereactant undergoing a Beckmann rearrangement reaction in the presence ofa catalyst. Exemplary catalysts include mieroporous and roesoporousnatural and synthetic molecular sieves, zeolites, aluminophosphate(AiPO) materials, and silicoalumlnophosphafe (SAPO) materials.

Silicoalumlnophosphate (SAPO) catalysts are synthetic molecular sievesknown to be useful as catalysts. Exemplary methods of preparing certainSAPO catalysts, are provided in U.S. Pat. No. 4,440,871 to Lok, et al,and N. Jappar, Y. Tanaka, S, Nakats, and T. Tatsumi, “Synthesis andCharacterization of a New Titanium Sllicoaluminophospate: TAPSO-37,”Microporous and Mesoporous Materials, Vol. 23, Issues 3-4, August 1998,pp. 189-178, the disclosures of each are hereby incorporated byreference.

An exemplary structure of one SAPO catalyst, SAPO-37, is illustrated inFIGS. 2A-2G. Molecular sieves, such as the SAPO-37 catalyst illustratedin FIG. 2A, are crystalline structures having a three-dimensionalframework of geometries. The frameworks of molecular sieves includecages, cavities, channels, and pores, depending on the type of molecularsieve. Acid sites either on the surface or in the interior or both ofthe molecular sieve provide the ability for some molecular, sieves toact as acid catalysts.

In the exemplary SAPO-37 structure shown in FIGS. 2A-2G, the portion 10of the catalyst includes a silicon-containing aluminophosphate geometrywith a faujasite-type structure. The geometry includes a plurality ofpores 12 connecting the interior cavities of the catalyst. FIGS. 2A-2Gfurther illustrate an acid site include a silicon atoms 14. In theinterior cavities of the catalyst. The acid sites further include ahydrogen atom, i.e. a proton 16, which is used in catalyzing theBeckmann rearrangement reaction. Silicon atom 14 and proton 18 areenlarged for identification in FIGS. 2A-2G. FIGS. 2A-2F illustrate avariety of perspective views of one interior cavity formed by thecatalyst 10. FIG. 2G shows an enlarged view of an acid site includingthe silicon atom 14 and proton 16 in the interior of the cage formed bythe catalyst 10.

As best shown in FIG. 2G, silicon atom 14 is illustratively attached tofour oxygen atoms 18A, 18B, 18C, and 18D, indicating it hasisomorphousiy been substituted for a phosphorous atom in the frameworkof the catalyst. Such an isomorphous substitution is referred to as atype-II substitution, in exemplary embodiments, the catalyst contains aplurality of these isomorphousiy substituted silicon atoms forming acidsites, such that the acid sites are discrete and well-isolated from eachother. This exemplary arrangement allows each acid site to function as awell isolated single-site Brønsted acid. Catalysts having a greaterfraction of type II isomorphous substitution acid sites are typified byhigher fractions of weak Brønsted acid sites. Higher silicon loadedcatalysts are typified by a greater fraction of strong acid sites, whichare attributable to type III substitution of two silicon atoms foradjacent aluminum and phosphorous atoms. Type ill substitution leads toa reduction in available weak Brønsted acid sites.

Proton 16 is illustratively attached to one of the oxygen atoms 18A. Theproton 16 can be given up by the acid site to catalyze a reaction in thecavity, such as a Beckmann rearrangement.

Typically, the catalyst is a silicon-containing aluminophosphate with afaujasite-type structure, in an exemplary embodiment, the catalyst is asilicon-containing aluminophosphate or silicoaluminophosphate catalystwith the international Zeolite Association (IZA) framework code FAU asdescribed in the Atlas of Zeolite Framework Types, 6th ed., ChristianBaerloeher, Lynne B. McCusker and David H. Olson, Elsevier, Amsterdam(2007), the disclosure of which is hereby incorporated by reference.More particularly, the catalyst is composed of sodalite cages linkedtogether through 6,6 (double-6) secondary building units. Twelve ofthese sodalite cages are then used to create a super-cage structure ofwhich the pore-aperture is 7.4 Å and the internal diameter of thesuper-cage is in the region of 12-14 Å. The catalyst further comprises aplurality of discrete Brønsted acid sites positioned in an interior ofthe framework, the acid sites comprising silicon isomorphousiysubstituted for phosphorous in the framework.

In exemplary embodiments, the catalyst is a silicoaluminophosphatehaving a microporous crystalline framework structure and whose essentialempirical chemical composition in the as-synthesized form on ananhydrous basis is:mR:(Si_(x)Al_(y)P_(z))O₂

wherein:

R represents at least one organic templating agent present in theintracrystaline pore system;

m has a value of from 0.02 to 0.3:

x, y, and z represent, respectively, the mole fraction of silicon,aluminum, and phosphorous present in the oxide moiety;

In one embodiment, the value of x, y, and z being within thecompositional area bounded by points A, B, C, D, and E of the ternarydiagram which is FIG. 3A representing the values set forth below inTable 1;

TABLE 1 Mole Fractions Corresponding to FIG. 3A Mole Fraction Point x yz A 0.01 0.47 0.52 B 0.94 0.01 0.05 C 0.98 0.01 0.01 D 0.39 0.60 0.01 E0.01 0.60 0.39

In another embodiment, the value of x, y, and z being within thecompositional area bounded by points a, b, c, d, and a of the ternarydiagram which is FIG. 3B representing the values set forth below inTable 2;

TABLE 2 Mole Fractions Corresponding to FIG. 3B Mole Fraction Point x yz a 0.02 0.49 0.49 b 0.25 0.37 0.38 c 0.25 0.48 0.27 d 0.13 0.60 0.27 e0.02 0.60 0.38

said silicoaluminophosphate having a characteristic X-ray powderdiffraction pattern which contains at least the d-spacing set forthbelow in Table 3.

TABLE 3 X-ray Powder Diffraction Pattern d-Spacing 2θ d RelativeIntensity 6.1-6.3 14.49-14.03 vs 15.5-15.7 5.72-5.64 w-m 18.5-18.84.80-4.72 w-m 23.5-23.7 3.79-3.75 w-m 26.9-27.1 3.31-3.29 w-m

One exemplary procedure for preparation of SAPO-37 catalysts is asfollows. First, an aluminum source, such as aluminum oxide, is slowlyadded to a phosphorous source, such as 85% phosphoric acid. A structuraltemplate solution is prepared by dissolving tetramethylammoniumhydroxide pentahydrate (TMAOH) in tetrapropylammonium hydroxide (TPAOH),to which fumed silica is slowly added. The solution is then addeddropwise with vigorous stirring to the aluminum/phosphorous mixture. Theresulting gel is heated to synthesize the desired structure. Theresulting product is isolated typically by centrifugation, filtering,and washing. The product is then dried, and calcined, prior to storagein an inert atmosphere.

The relative loadings of silicon and aluminum can be adjusted to providea suitable quantity and distribution of acid sites on the surface of andin the inferior of the catalyst. Exemplary procedures for adjusting thequantity and distribution of acid sites include adjusting the ratio ofsilicon to phosphorous provided in forming the gel in typicalembodiments, the gel ratio of Si:P is from about 0.1:1 to about 0.8:1,in a more particular embodiment, the gel ratio of Si:P is from about0.11:1 to about 0.63:1. In still other embodiments, the gel ratio ofSi:P is as little as 0.1:1, 0.11:1, 0.18:1, 0.17:1, 0.21:1, 0.22:1, oras great as 0.42:1, 0.83:1, 0.75:1, 0.8:1, or within any range definedbetween any pair of the foregoing values.

The weight percentage of silicon in the formed catalyst can also bedetermined. An exemplary method for determining the weight percentage ofsilicon is by inductively coupled plasma. Typically, silicon comprisesfrom about 1 wt % to about 10 wt % of the total weight of the catalyst.In a more particular embodiment, silicon comprises from about 2 wt % toabout 9.1 wt % of the total weight of the catalyst. In still otherembodiment, silicon comprises a weight percentage of the total weight ofthe catalyst up from as little as 1 wt %, 1.5 wt %, 2 wt %, 2.1 wt %,2.6 wt % to as much as 6 wt %, 7 wt %, 8 wt %, 9 wt % 9.1 wt %, 10 wt %,or within any range defined between any pair of the foregoing values.

Oximes are converted to lactams, such as in the examples illustrated inFIGS. 1A and 1B, through contact with the catalysts. The presentdisclosure is believed to be generally applicable to any oxime generatedfrom a variety of aldehydes and ketones. Exemplary oximes include, butare not limited, to cyclohexanone oxime, cyclododecanone oxime,4-hydroxy acetophenone oxime and oximes formed from acetophenone,butyraldehyde, cyclopentanone, cycloheptanone, cyclooctanone,benzaldehyde.

In exemplary embodiments, the reaction is performed in the presence of asolvent. Although working examples are provided for reactions performedin a solvent, the present disclosure is believed to also be applicablefor Beckmann rearrangement reactions performed in the absence of asolvent, in reactions performed in the absence of a solvent, the productis used to absorb the exothermic beat produced by the reaction. In theseembodiments, a large ratio of lactam to oxime is maintained in thereaction area to absorb the energy produced by the reaction.

Exemplary solvents include organic nitriles of the formula:R¹—CN

Wherein R¹ represents C₁-C₈-alkyl, C₁-C₈alkenyl, C₁-C₈-alkynyl,C₃-C₈-cycloalkyl; C₃-C₈-aralkyl including a C₈ aromatic ring. Exemplarynitrites include acetonitrile, benzonitrile and mixtures of any of theforegoing.

Other exemplary solvents include aromatic compounds of the formula:R²—Ar

Wherein Ar is an aromatic ring and R² represents H, F, Cl, or Br,Exemplary aromatic solvents include benzene and chlorobenzene.

Still other exemplary solvents include water and alcohols of theformula:R³—OH

Wherein R³ represents a hydrogen, C₁-C₈-alkyl, C₁-C₈-alkenyl,C₁-C₈-alkynyl, C₃-C₈-cycloalkyl; C₃-C₈-arylalkyl. Exemplary alcoholsinclude alcohols of 8 or fewer carbon atoms such as methanol, ethanol,n-propanol, iso-propanol, n-butanol, see-butanol, isobutanol,tert-butanol, n-amyl alcohol, n-hexanol, phenol, and mixtures of any ofthe foregoing.

In exemplary embodiments, the solvent is rigorously dried prior tocontact with the catalyst. As used herein, rigorously dried isunderstood to mean dried to a level of 100 ppm water or less. Exemplarymethods of drying include adsorption of water using molecular sieves,such as Activated 4A molecular sieves. As used herein, a reactionperformed in the absence of water means a reaction in which watercomprises less than 0.01 wt % of the weight of the reactants.

The reaction is performed as a liquid phase reaction or a gas phasereaction. As used herein, a liquid phase reaction in a reaction in whichsubstantially ail of the oxime is in the liquid phase when reacted toform the lactam. As used herein, a gas phase reaction in a reaction inwhich substantially all of the oxime is in the gas or vapor phase whenreacted to form the lactam.

When performed as a gas phase reaction, the reaction is typicallyperformed at a temperature-beneath 350° C. In a more particularembodiment, the reaction is performed at a temperature from about 130°C. to about 300° C. in still other embodiments, the reaction may beperformed at a temperature as low as about 90° C., 100° C., 110° C.,120°, 130°, or as high as about 140° C., 150° C., 170° C., 180° C., 190°C., 200° C., 210° C., 220° C., 230° C., 240° C. 250° C., 275° C., 300°C., 325° C., 350° C., or within any range defined between any pair ofthe foregoing values.

When performed as a gas phase reaction, the reaction is typicallyperfored at a pressure from about 0.1 bar to about 1 bar. Moreparticularly, in exemplary embodiments of the reaction performed as agas phase reaction, the pressure may be as low as 0.01 bar, 0.02 bar,0.05 bar, 0.1 bar, as high as 0.5 bar, 1 bar, or within a range definedbetween any pair of the foregoing values.

When performed as a liquid phase reaction, the reaction is typicallyperformed at a temperature beneath 250° C., in a more particularembodiment, the reaction is performed at a temperature from about 130°C. to about 190° C. in still other embodiments, the reaction may beperformed at a temperature as low as about 90° C. 100° C., 110° C.,120°, 130°, or as high as about 140° C., 150° C., 170° C., 180° C., 190°C., 200° C., 210° C., 220° C., 230° C., 240° C. 250° C., or within anyrange defined between any pair of the foregoing values.

When performed as a liquid phase reaction, the reaction is typicallyperformed at a pressure from about 1 bar to about 5 bar. Moreparticularly, in some exemplar) embodiments, the pressure may be as lowas 0.5 bar, 1 bar, as high as 1 bar, 2 bar, 5 bar, 10 bar, 15 bar, 20bar, 25 bar, 30 bar, 35 bar, or within any range defined between anypair of the foregoing values, in some exemplary embodiments of thereaction performed as a liquid phase reaction, the solvent is typicallya gas at the reaction temperature, but is maintained in the liquid phaseby performing the reaction at an elevated pressure.

When performed as a liquid phase reaction, the reaction is typicallyperformed at a temperature and pressure below the critical point of thesolvent, where the pressure may be as low as 1 bar as high as 2 bar, 5bar, 10 bar, 15 bar 20 bar, 25 bar, 30 bar, 35 bar, or within any rangedefined between any pair of the foregoing values.

The efficiency of the reaction may be expressed in terms of conversionof oxime, selectivity of the desired product, or yield. Conversion is ameasure of the amount of oxime reactant that is consumed by thereaction. Higher conversions are more desirable. The conversion iscalculated as:

${{Conversion}(\%)} = {100\% \times \left( {1 - \frac{{moles}\mspace{14mu}{of}\mspace{14mu}{oxime}\mspace{14mu}{produced}}{{moles}\mspace{14mu}{of}\mspace{14mu}{oxime}\mspace{14mu}{supplied}}} \right)}$

Selectivity is a measure of the amount of the desired product that isproduced relative to all reaction products. Higher selectivities aremore desirable. Lower selectivities indicate a higher percentage ofreactant being used to form products other than the desired lactam. Theselectivity is calculated as:

${{Selectivity}(\%)} = {100\% \times \frac{{moles}\mspace{14mu}{of}\mspace{14mu}{desire}\mspace{14mu}{lactam}\mspace{14mu}{produced}}{{total}\mspace{14mu}{moles}\mspace{14mu}{of}\mspace{14mu}{product}\mspace{14mu}{produced}}}$

Yield is a measurement that combines selectivity and conversion. Yieldindicates how much of the incoming oxime is reacted to form the desiredlactam. The yield is calculated as:Yield (%)=Selectivity (%)×Conversion (%)/100%

The methods according to the present disclosure result in highconversions and selectivities.

In typical embodiments, the conversion is 50% or higher. In a moreparticular embodiment, the conversion is from about 50% to about 100%.For example, the conversion may be as low as about 50%, 60%, 70%, 75%,or as high as about 80%, 85%, 90%, 95%, 97.5%, 99%, 99.5%, approaching100%, or 100%, or may be within any range defined between any pair ofthe foregoing values.

In typical embodiments, the selectivity is 50% or higher. In a moreparticular embodiment, the conversion is as low as about 50%, 55%, 60%,65%, or as high as about 70%, 75%, 80%, 85%, 90%, 95%, 97.5%, 99%,99.5%, approaching 100%, or may be within any range defined between anypair of the foregoing values.

In typical embodiments, the conversion of cyclohexanone oxime toε-caprolactam is from about 90% to about 100% and the selectivity isfrom about 80% to about 100%. In more particular embodiments, theconversion is from about 95% to about 100% and the selectivity is fromabout 90% to about 98%. In still more particular embodiments, theconversion is from about 98% to approaching 100% and the selectivity isfrom about 95% to about 98%.

In typical embodiments, the conversion of cyclododecanone oxime toω-laurolactam is from about 90% to about 100% and the selectivity isfrom about 80% to about 100%. In more particular embodiments, theconversion is from about 95% to about 100%, and the selectivity is fromabout 98% to about 99%.

Example 1—Preparation of SAPO-37 Catalyst

A pseudo-boehmite phase of aluminum oxide was slowly added to a dilutedsolution of phosphoric acid (85 wt %) and left to stir for 7 hours. Asecond solution of tetramethylammonium hydroxide pentahydrate (TMAOH)dissolved in tetrapropylammonium hydroxide (TPAOH) (40 wt %) wasprepared to which fumed silica was slowly added. This was left to stirfor 2 hours and was then added dropwise to a stirredaluminum/phosphorous gel. SAPO-37 catalysts were prepared with fourdifferent loadings of SiO₂. The catalysts were labeled based on theratio of SiO₂ to H₃PO₄ used in the preparation. Gel loadings for thevarious samples can be found in Table 4 below.

TABLE 4 Gel loadings for SAPO-37 materials Sample Gel compositionSAPO-37 1.00H₃PO₄:0.67Al₂O₃:0.97TPAOH:0.025TMAOH:0.11SiO₂ (0.11) SAPO-371.00H₃PO₄:0.67Al₂O₃:0.97TPAOH:0.025TMAOH:0.21SiO₂ (0.21) SAPO-371.00H₃PO₄:0.67Al₂O₃:0.97TPAOH:0.025TMAOH:0.42SiO₂ (0.42) SAPO-371.00H₃PO₄:0.67Al₂O₃:0.97TPAOH:0.025TMAOH:0.63SiO₂ (0.63)

The mixture stirred for 68 hours and was then transferred to anautoclave. The solution was heated under autogenous pressure at 200° C.for 24 hours. On removal the gel was centrifuged, filtered and washed.The material was then dried overnight at room temperature. The whitesolid was then calcined at 550° C. for 16 hours and kept in an inertatmosphere.

Example 2—Characterization of Catalysts

²⁹Si Solid State NMR

All NMR measurements were performed on a Chemagnetics infinity 400spectrometer on a 4 mm magic angle spinning (MAS) double-resonanceprobe. The sample was packed in a thin wall zirconium oxide rotor andspun at 8 kHz using compressed nitrogen to prevent sample degradation inair. ²⁷Al NMR: all experiments were performed using direct acquisition.³¹P NMR data were acquired both with direct acquisition (120 s delaybetween scans) and with cross-polarization. ²⁹Si HMR data for all 1Dexperiments were performed using ramped cross-polarization with SPINAL64decoupling during acquisition. Two dimensional experiments wereperformed using proton driven spin diffusion (PDSD) with a mixing timeof 5 ms.

The results of the HMR measurements can be seen in FIG. 4. FIG. 4A showsthe results of 2D MAS ²⁹Si HMR of SAPO-37 (0.21). FIG. 4B shows theresults of 2D MAS ²⁹Si HMR of SAPO-37(0.63). FIG. 4C shows the resultsof MAS ²⁹Si HMR of SAPO-37 systems of different gel-ratios, FIG. 4Cshows the presence of isolated Si(OAl)₄ sites at −93 ppm andSi(OAl)₃(OSi) sites at −98 ppm.

FIGS. 4A-4C illustrate that silicon begins to cluster at higherloadings. FIG. 4A shows low to no peaks at −103 ppm corresponding to acluster of two sites, and at −108 ppm, corresponding to a cluster ofthree sites. As illustrated in FIGS. 4B and 4C, at higher levels ofsilicon loading, the silicon begins to cluster, forming peaks at −103ppm-Si(OAl)₂(OSi)₂ and −108 ppm, Si(OAl)(OSi)₃. Lower silicon loadings,such as using SAPO-37 (0.21) as shown in FIGS. 3A and 3C, reduces thepeak at −98 ppm, indicating a higher prevalence of isolated single siteswith weak Brønsted acidity over clusters of multiple sites.

NH₃—Temperature Programmed Desorption (TPD)

The quantity and strength of acid sites was investigated usingtemperature programmed desorption (TPD) of ammonia. As-synthesizedmaterials were pretreated in a 20% O₂ in He mixture and heated at 10°C./min to 550° C. and held at 550° C. for 2 hours. Desorption wasperformed at 10° C./min to 600° C. for 40 minutes.

In this experiment, ammonia is adsorbed onto the surface of thecatalyst, binding to the acid sites, giving a defined peak. The area ofthis peak corresponds to the quantity of ammonia in the system. Thesystem is then heated and the ammonia desorbs with the temperature. Thestronger the acid site, the higher the temperature required to desorbthe ammonia.

The total acidity values for SAPO-37(0.21) and SAPO-37(0.42) obtained byNH₃-TPP were within experimental error. As shown in FIG. 5, the totalnumber of acid sites, as measured by total mmol/g of desorbed NH₃,showed that SAPO-37(0.21) and SAPO-37(0.42) had similar amounts of acidsites, while with SAPO-37(0.83) showed far fewer acid sites than eitherSAPO-37(0.21) or SAPO-37(0.42). Analyzing the temperature regionsindicates the relative strength of the acid sites present, with strongersites requiring higher temperatures for desorption. As shown in FIG. 5,the lower loading materials SAPO-37(0.21) and SAPO-37(0.42) had moreweak acid sites as shown by the higher values at lower temperatures, butincreased silicon loading lead to a decrease in weak acid sites and anincrease in strong acid sites. These results are consistent with thesilicon clustering results suggested by the NMR data in FIGS. 4A-4C.

FT-IR, CO Probe

The number and strength of acid sites were further investigated usingFT-IR spectra from a carbon monoxide (CO) probe. Samples of each testedcatalyst were ground and pressed into self-supporting pellets. Thepellets were then heated at 10° C./min to 550° C. in flowing gascomprising 20% O2/80% N2, then held at temperature for 1 hour. Gas flowwas then switched to helium and held for additional 1 hr. The sampleswere cooled to 30° C. and the spectrum recorded. Nine 0.02 cc infectionsof CO were added to the samples, followed by 1 final 0.2 cc injection.Following each injection, the system was equilibrated for 3 min beforethe spectrum was recorded. All spectra were recorded on a Nicolet Nexus870 IR spectrometer, with 128 scans using a cooled MCT detector. Allspectra were processed using the GRAMS/Al 9 software available fromThermo Scientific.

The results, of FT-IR, CO probe testing are presented in Table 5.

TABLE 5 FT-IR, CO probe results System CO area/au Peak shift/cm⁻¹SAPO-37 (0.21) 0.854 305 SAPO-37 (0.42) 0.856 311 SAPO-37 (0.63) 0.582321

Table 5 shows that the total acidity, as indicated by the COarea/arbitrary unit (au) is:SAPO-37(0.21)˜SAPO-37(0.42)>SAPO-37(0.63)

The peak shift gives an insight into the acid strength, where a highershift corresponds to stronger acid sites. Table 5 shows that in terms ofacid strength:SAPO-37(0.63)>SAPO-37(0.42)>SAPO-37(0.21)

Both the NH₃-TPD and FT-IR CO probe data suggest that SAPO-37(0.21) hasthe same quantity of acid sites as SAPO-37(0.42), and that SAPO-37(0.63)has fewer acid sites than either SAPO-37(0.21) or SAPO-37(0.42).Similarly, both the NH₃-TPD and FT-IR CO probe data suggest thatSAPO-37(0.63) has the strongest acid sites and SAPO-37(0.21) has theweakest. The NH₃-TPD suggested that SAPO-37(0.21) and SAPO-37(0.42) hadmore weak sites (desorption at 200-300° C. and 300-400° C.) thanSAPO-37(0.63), but SAPO-37(0.63) had more strong acid sites (400-500°C.) than either SAPO-37(0.21) or SAPO-37(0.42).

FT-IT, Collidene Probe

The number and strength of acid sites were further investigated usingFT-IR spectra from a collidene probe. Samples were ground and pressedinto self-supporting pellets. The pellets were then heated at 10° C./minto 550° C. in flowing 20% O2/N2, then held at temperature for 2 hours.The samples were cooled to 30° C. and the spectrum recorded. Collidenewas adsorbed at 150° C. for 1 hr. Collidene was then desorbed at150/300/450° C. for 1 hr each step. All spectra were recorded on aNicolet Nexus 870 IR spectrometer, with 128 scans using a cooled MCTdetector. All spectra were processed using the GRAMS/Al 9 softwareavailable from Thermo Scientific.

In this experiment, collidene is adsorbed onto the surface of thecatalyst, binding to the acid sites, giving a defined peak. The area ofthis peak corresponds to the quantity of collidene in the system. Thesystem is then heated and the collidene desorbs with the temperature.The stronger the acid site, the higher the temperature required todesorb the collidene. Weak sites are characterized as collidene desorbsbetween 150° and 300° C., medium sites are characterized as collidenedesorbs between 300° and 450° C., and strong sites are characterized asstill having collidene adsorbed at 450° C.

The results of FT-IR collidene probe testing are presented in Table 6.

TABLE 6 FT-IR, collidene probe results System Weak sites Medium sitesStrong sites Total sites SAPO-37 (0.21) 0.913 2.845 1.609 5.367 SAPO-37(0.42) 0.389 2.722 1.593 4.704 SAPO-37 (0.63) 0.382 2.420 1.501 4.303

Table 6 shows that the total acidity as measured by the total number ofacid sites is:SAPO-37(0.83)>SAPO-37(0.42)>SAPO-37(0.21)

Regarding the strength of the acid sites, the weak and medium sites bothshowed higher numbers for the SAPO-37(0.21) than SAPO-37(0.63). Thelarge number of weak sites for SAPO-37(0.21), 0.913 out of 5.367 totalsites, accounted for more than 15% of the total. This was much higherthan for SAPO-37(0.42), which had 0.389 out of 4.704 or 8.3% of thetotal and SAPO-37(0.83), which had 0.382 out of 4.303 or 8.9% of thetotal, and suggests a large proportion of Brønsted acid sites that arediscrete and of a single-site nature. The strength of the SAPO-37(0.42)weak acid sites and the SAPO-37(0.83) for strong acid sites does notperfectly align with the other acid investigations, but the medium sitedata is nearly equivalent for SAPO-37(0.21) and SAPO-37(0.42).

The greater fraction of weak Brønsted acid sites is attributable to agreater proportion of type II isomorphous substitutions of silicon forphosphorous in the catalyst framework. Catalysts with higher siliconloadings are typified by greater proportion of strong acid sites thatare attributable to type III substitutions, which lead to a reduction inthe proportion of weak Brønsted acid sites.

The SAPO-37 unit cell was optimized using CRYSTAL09 package to performab initio calculations of crystal system, R. Dovesi, R. Orlando, B.Civalleri, C. Roetti, V. R. Saunders, and C. M. Zicovich-Wilson, Z.Kristallogr. 220, 571 (2005). The SAPO-37 unit cell contained 577 atomswith the formula H₁Si₁Al₉₆P₉₅O₃₈₄. This corresponds, to a 1 mol %loading of silicon. A unit cell was modeled with NH₃ present such thatit could interact with the acid site (H₄N₁Si₁Al₉₆O₃₈₄). Using thefollowing equation the binding energy of NH₃ with SAPO-37 was estimatedto be 117 kJ mol⁻¹:E _(bind) =E(SAPO-37+NH₃)−E(SAPO-37)−E(NH₃)

The above calculation may be used as a measure of acidity. The resultsare in the expected range for these calculations.

Powder X-Ray Diffraction and BET Surface Area

Powder X-Ray diffraction patterns were obtained using a Siemens D5000diffractometer where λ=1.54058 angstrom (Å) with Cu K_(α)1 radiation, inaddition, an X-ray diffraction pattern of the catalyst SAPO-5 (AFI) wasobtained. The three higher loading samples were found to be phase-pure,but SAPO-37(0.11) showed a significant AFI impurity phase. TheSAPO-37(0.11) showed peaks corresponding to both FAU-type framework at111 and 331, as well as IZA AFI-type framework at 100 and 200. Theresults of powder X-ray diffraction can be found in FIG. 6.

BET surface area measurements to investigate the total surface area ofthe catalysts were performed using a Gemini 2375 surface area analyzerand prepared using flow gas preparation. The results of BET surface areameasurements and estimated silicon content in wt % can be found in FIG.7. The unit cell determinations provided similar unit cell sizes for thethree measured SAPO-37 catalysts, although the larger loadings of SiO₂resulted in slightly larger unit, cells, providing additional evidencefor increased silicon substitution in the molecular sieve framework.

The XRD and BET results were typical for this system.

Inductively Coupled Plasma (ICP)

ICP measurements were taken to quantify the actual weight percentage ofsilicon in each of the prepared catalyst. A Perkin-Elmer Optimum 3000 DVwas used to provide ICP results. Calcined samples were prepared andfully digested in 10 ml of deionized water and 10 ml of ACS PlusCertified sulfuric acid available from Fisher Scientific. Solutions ofstandard concentrations were used for calibration.

The ICP results and ratio of silicon to phosphorous loadings in the gelformed in Example 1 can be found in Table 7 below:

TABLE 7 ICP results Si/P Gel ratio Si/wt % System from synthesis gelFrom ICP measurements SAPO-5 (AFI) 0.21 1.33 SAPO-34 (CHA) 0.23 0.73SAPO-BER 0.21 0.73 SAPO-37 (0.21) 0.21 2 SAPO-37 (0.63) 0.63 9.1

The ratio of silicon to phosphorous in the gel used to form thecatalysts for SAPO-37(0.83) and SAPO-37(0.21) was 0.63:0.21, or 3:1. Thesilicon weight percentage of SAPO-37(0.63) was higher than the siliconweight percentage of SAPO-37(0.21). The ratio of silicon weightpercentage between SAPO-37(0.63) and SAPO-37(0.21) was 9.1:2, or 4.55:1.This was higher than the gel loading ratio of 3:1.

Scanning Electron Microscopy Images

Scanning Electron Microscopy images of the catalysts were obtained usinga JOEL-JSM5910 microscope with accelerating voltage of 0.3-30 kV. Thesamples were prepared by gold costing, SEM revealed that all 3 systemsconsisted, of regular octahedral crystals of roughly 1 μm in length. AnSEM image of SAPO-37(0.21) is provided as FIG. 8A, an SEM image ofSAPO-37(0.42) is provided as FIG. 8B, and an SEM image of SAPO-37(0.83)is provided as FIG. 5C.

Example 3—Gas Phase Catalysis Preparation of Catalysis

The gel loadings for the catalysts used in the gas phase examples isgiven in Table 8.

TABLE 8 Gel loadings for SAPO materials Sample Gel composition SAPO-52.0 H₃PO₄:1.0 Al₂O₃:0.4 SiO₂: 2.0 Triethylamine:50.0 H₂O HSAPO-37 (0.42)1.00H₃PO₄:0.67Al₂O₃:0.97TPAOH: 0.025TMAOH:0.42SiO₂ MSAPO-37 (0.22)1.00H₃PO₄:0.69Al₂O₃:2.40 TPAOH: 0.026TMAOH:0.22SiO₂:6.96 H₂O LSAPO-37(0.17) 1.00H₃PO₄:0.68Al₂O₃:2.40 TPAOH: 0.026TMAOH:0.17SiO₂:7.12 H₂OSAPO-11 2.0 H₃PO₄:1.0 Al₂O₃:0.4 SiO₂:2.0 Pr₂NH:50.0 H₂O SAPO-41 2.0H₃PO₄:1.0 Al₂O₃:0.4 SiO₂:2.0 Pr₂NH:50.0 H₂O

The SAPO-37 catalysts were made as in Example 1.

SAPO-5 was prepared by diluting 4.7 g of H₃PO₄ (85% in H₂O) in a Teflonbeaker with 10 ml of H₂O and stirred until homogeneous (5 minutes). 4.3g of Al(OH)₃ was slowly added to the acid, followed by a further 10 mlof H₂O. The mixture was stirred for 10 minutes. 0.76 g of fumed silicawas slowly added, followed by 10 ml of H₂O. The mixture was stirred for30 minutes. Finally the templating agent (N-Methyl-dicyclohexyl-amine)was added dropwise and a further 10 ml of H₂O was added. The mixture wasstirred for 1 hour. The white gel was then transferred to an autoclaveand heated to 200° C. for 2 hours. On removal, the gel was filtered andwashed with H₂O and left to dry at 70° C. overnight. The white solidproduced was calcined at 550° C. for 10 hours before use.

SAPO-TRY was prepared in the same manner as the SAPO-5 above, exceptthat no templating agent was used.

The SAPO-34 catalyst was prepared according to the method provided by D.Dubois, et al., Fuel Process. Technol. 2003, 83, 203, the disclosures ofwhich are hereby incorporated by reference.

TS-1, a titanium silicalite zeolite-based catalyst was obtained from theNational Chemical laboratory, Pune India. The sample has a Ti loading of2 wt %. The TS-1 catalyst is disclosed in U.S. Pat. No. 4,859,785, thedisclosure of which is hereby incorporated by reference.

Analysis and Conversion and Selectivity

The conversion and selectivity of the system was analyzed using a Clarus400 gas chromatogram with FID and using an Elite 5 column, the peakareas were calibrated using known response factors. The method was:start at 120° C., hold for 2 minutes, then ramp at 15° C./min up to 220°C., and hold for 5 minutes at 220° C. The method was 13 minutes and 40seconds long in total. The cyclohexanone oxime has a peak correspondingto a retention time of 4.0 minutes, ε-caprolactam peak has a peakcorresponding to a retention time of 5.8 minutes, the by-product has apeak corresponding to a retention time of 6.6 minutes. The injector portwas set to 220° C. and the detector was set to 250° C. The carrierpressure (Helium) was 14 psig. The method was given 1 minute toequilibrate before injection. A centrifuged sample of 5 μl was injected.

The samples were calibrated using a relative response factor ofε-caprolactam relative to cyclohexanone oxime, which was found to be1.119. The samples were calibrated to an internal standard ofchlorobenzene for the mass balance. Cyclohexanone oxime was found tohave a relative response factor of 1.2972 relative to chlorobenzene, andε-caprolactam was found to have a response factor of 1.4518 relative tochlorobenzene. The mass balance at 130° C. was found to be 106% after 6hours. Using the following formula, the response factors were used tocalculate the moles of cyclohexanone oxime, ε-caprolactam, andby-products (response factor assumed to be 1.00):

$\frac{{Moles}\lbrack A\rbrack}{{Moles}\lbrack B\rbrack} = {{Relative}\mspace{14mu}{Response}\mspace{14mu}{Factor} \times \frac{{Area}\lbrack A\rbrack}{{Area}\lbrack B\rbrack}}$Experimental Procedure

A cylindrical glass tube (4 mm in diameter) with a glass frit was packedwith a 5 mm layer of glass beads, a layer of pelletized catalyst (˜0.25g, 40 mm) and a further 60 mm layer of glass beads, was placed inside aflow reactor heated by a jacket to 673 K. The sample was then treatedunder a flow of Helium gas for 1 hour. The temperature was dropped tothe test temperature as set forth below and a liquid feed of 10 wt %cyclohexanone oxime in ethanol was fed into the reactor, maintaining theexperimental weight hour space velocity (WHSV) as set forth below.

Comparison of Catalysts of WHSV 0.3 hr⁻¹ and 300° C.

Gas phase runs were made for various catalysts under similar conditions.The conditions selected were a WHSV of 0.3 hr⁻¹, a liquid feed of 10 wt% oxime in ethanol, a temperature of 300° C., helium flow of 33.3mL/min, and 0.25 g of catalyst. Each catalyst was pre-activated at 400°C. for 1 hour in a 33.3 mL/min flow of helium. Samples were taken forconversion and selectivity analysts after an hour.

The results can be found in Table 9 and FIG. 9.

TABLE 9 Gas phase results ε-caprolactam System Conversion/mol %selectivity/mol % SAPO-37 (0.42) 99.7 86.2 SAPO-5 66.0 53.8 SAPO-34 78.275.2 SAPO-TRY 74.9 79.0

The SAPO-37 (0.42) catalyst produced much higher conversion andselectivity results than any of the other SAPO catalysts tested.

Comparison of SAPO-37 Catalysts with SAPO-41 and TS-1 at VariousTemperatures

As a comparison, gas phase runs were made for SAPO-37, SAPO-41, and TS-1catalysts under similar conditions. The conditions selected were a WHSVof 0.3 hr⁻¹, a liquid feed of 10 wt % oxime in ethanol, a helium flow of33.3 ml/min, and 0.25 g of catalyst. Each catalyst was pre-activated at400° C. for 1 hour in a 33.3 mL/min flow of helium. Samples were takenfor conversion and selectivity analysts after an hour. The results forvarious temperatures are provided in FIGS. 10-13.

The results for SAPO-37(0.22) are shown in FIG. 10, SAPO-37(0.22)resulted in high conversions and selectivity. Conversion increased astemperature increased from 300° to 350°. Selectivity also increased, butwas above 80% in at all three measured temperatures.

The results for SAPO-37(0.42) are shown in FIG. 11, SAPO-37(0.22)resulted in high conversions and selectivity. Conversion and selectivitydecreased as temperature increased from 300° to 325°. However,conversion remained high at 94.6% and selectivity remained above 80%.

As shown in FIG. 12, the SAPO-41 provided high conversion, but muchlower selectivity to the ε-caprolactam than the SAPO-37 catalysts.

The results for TS-1 are shown in FIG. 13. Conversion and selectivitywere high for TS-1 at 300° C.

FIGS. 14 and 15 compare the results from the various catalysts at thesame temperatures.

As can be seen in FIG. 14, at 300° C., high selectivity and conversionwere obtained for SAPO-37 (0.42) compared to the SAPO-41 catalyst.

As shown in FIG. 15, all three SAPO catalysts gave good conversion at325° C. However, only the SAPO-37 catalysts gave high selectivities.

Example 4—Liquid Phase Catalysis Preparation of Catalysis

The gel loadings for the catalysts used in the gas phase examples isgiven in Table 10.

TABLE 10 Gel loadings for SAPO materials Sample Gel composition SAPO-52.0 H₃PO₄:1.0 Al₂O₃:0.40 SiO₂:2.0 TEA:50 H₂O SAPO-34 2.0 H₃PO₄:1.0Al₂O₃:0.30 SiO₂:2.0 TEAOH:50 H₂O (CHA) SAPO-371.00H₃PO₄:0.67Al₂O₃:0.97TPAOH:0.025TMAOH:0.21SiO₂ (0.21) SAPO-371.00H₃PO₄:0.67Al₂O₃:0.97TPAOH:0.025TMAOH:0.42SiO₂ (0.42) SAPO-41 2.0H₃PO₄:1.0 Al₂O₃:0.4 SiO₂:2.0 Pr₂NH:50.0 H₂O

The SAPO-37 catalysts were made as in Example 1.

The SAPO-5 and SAPO-34 catalysts were made as in Example 3.

The SAPO-11 catalyst was made according to P. Meriaudeau, V. A. Tuan, V.T. Nghiem, S, Y. Lai, L. N. Hung and C. Naccache, Journal of catalysis,1997, 169, 55-66, the disclosure of which is hereby incorporated byreference.

The SAPO-41 catalyst was made according to P. Meriaudeau, V. A. Tuan, V.T. Nghiem, S. Y. Lai, L. N. Hung and C. Naccache, Journal of catalysis,1997, 169, 56-66, the disclosure of which is hereby incorporated byreference.

Experimental Procedure

100 mg of cyclohexanone oxime, 100 mg of catalyst and 20 ml ofbenzonitrile as solvent (Aldrich) were added to a glass reactor andstirred at 500 rpm at the selected temperature under reflux. Sampleswere taken at predetermined intervals based on the selected temperature:30 minutes for 130° C., 15 minutes for 150° C., 5 minutes for 170° C.,and 5 minutes for 190° C. All samples were analysed on a Varian Star3400CX gas chromatogram with flame ionization detector (FID). Sampleswere injected into a Perkin Elmer a HP1 cross linked methylsiloxane (30m×0.32 mm×1 μm film thickness) column. The samples were mass balancedusing chlorobenzene as an internal standard.

Analysis of Conversion and Selectivity

The samples were analyzed as in Example 3, with benzonitrile solventpeak having a large peak corresponding to a retention time of 3.5minutes.

Comparison of Catalysis at 130° C.

Liquid phase runs were made for various catalysts under similarconditions. The conditions selected were 130° C., with acatalyst:cyclohexanone oxime:benzonitrile ratio of 1:1:200, and 0.1 g ofcyclohexanone oxime. The samples were analyzed after 7 hours.

The results can be found in Table 11 and FIG. 16.

TABLE 11 Liquid phase results IZA framework Pore Conversion/ε-caprolactam System code diameter mol % selectivity/mol % SAPO-5 AFI7.3 Å × 7.3 Å 33.2 65.9 SAPO-34 CHA 3.8 Å × 3.8 Å 18.6 87.3 SAPO-37 FAU7.4 Å × 7.4 Å 98.8 90.3 (0.42) SAPO-41 AFO 7.0 Å × 4.3 Å 23.5 68.1

The SAPO-37 and SAPO-5 frameworks have similar pore diameters, theformer 7.4 Å, the latter 7.3 Å, yet they showed very different levels ofactivity, therefore the environments were probed using ²⁹Si MAS NMRtechniques. The SAPO-37 spectrum showed a dominant peak at −93 ppm, witha smaller secondary peak at −98 ppm, corresponding to Si(OAl)₄ andSi(OSi)(OAl)₃ environments respectively. The Si(OAl)₄ environment showsthat the silicon has substituted a single phosphorus atom, thereforegenerating a Brønsted acid site (a type II substitution mechanism), theSi(OSi)(OAl)₃ environment shows that two silicons have substituted aphosphorus and aluminium pair, therefore not generating an acidify (typeIII substitution mechanism). In contrast the SAPO-5 spectrum showed adominant peak at −110 ppm, corresponding to a Si(OSi)₄ environment,suggesting the silicon was present mostly in siliceous zones. Thisshowed that the isolated silicon sites are the active site for thisreaction. The silicon content of the SAPO-37 species was varied (denotedSAPO-37(X) where X is the assynthesised gel ratio), giving threedifferent samples, which showed subtle differences in catalyticperformance.

Both SAPO-37 catalysts showed very high conversion and selectivity,especially when compared to the other SAPO catalysts.

Liquid Beckmann Rearrangement Using Chlorobenzene Solvent

The same experimental procedure as for the liquid reactions withbenzonitrile were performed with chlorobenzene as a solvent. Thereaction was performed at 130° C., with 100 mg of cyclohexanone oxime,10.0 mg of SAPO-37(0.21) catalyst, and 20 ml of chlorobenzene. After 7hours, 14.6% conversion of oxime and 95.0% selectivity for ε-caprolactamwere observed.

Progression of Reaction Over Time for Various Catalysts at 130° C.,

The conversion, selectivity, and yield over time of a reaction with aSAPO-37 (0.16) catalyst, a SAPO-11 catalyst, and a SAPO-41 catalyst at130° C. are illustrated in FIGS. 17-20. The SAPO-37 catalyst showed veryhigh conversion and selectivity compared to the other SAPO catalysts.

FIG. 17 illustrates the high conversion and selectivity using theSAPO-37 (0.16) catalyst in a liquid phase reaction using benzonitrile assolvent. The reaction was performed at 130° C., with acatalyst:cyclohexanone oxime:benzonitrile ratio of 1:1:200, with 0.1 gof cyclohexanone oxime used, and performed for 7 hours.

FIG. 13 illustrates the same reaction using anhydrous benzonitrile assolvent. The reaction was performed at 130° C., with acatalyst:cyclohexanone oxine:anhydrous benzonitrile ratio of 1:1:200,with 0.125 g of cyclohexanone oxime used, and performed for 7 hours.

The anhydrous benzonitrile shown in FIG. 18 resulted in greaterselectivity but lower conversion than the (wet) benzonitrile shown inFIG. 17. Both FIGS. 17 and 18 show high conversion and selectivity in aliquid phase reaction.

FIG. 19 illustrates a lower conversion and selectivity for a liquidphase reaction with SAPO-11 as the catalyst. The reaction was performedat 130° C. with a catalyst:cyclohexanone oxime:benzonitrile ratio of1:1:200, with 0.1 g of cyclohexanone oxine used, and run for 7 hours.

FIG. 20 illustrates an even lower conversion and selectivity for aliquid phase reaction with SAPO-41 as the catalyst. The reaction wasperformed at 130° C., with a catalyst:cyclohexanone oxime:benzonitrileratio of 1:1:200, with 0.1 g of cyclohexnone oxime used, and run for 7hours.

Further liquid test results are provided in Tables 12 and 13. Table 12presents the conversion, selectivity, and yield for SAPO-37 catalystswith various gel loadings at time intervals during the reaction. Table13 presents the final conversion and selectivity values taken for eachcatalyst at the indicated temperature. Benzonitrile was used as thesolvent in each of the runs in Tables 12 and 13, SAPO-37(0.21)ANdesignates the use of anhydrous benzonitrile as the solvent.

TABLE 12 Conversion and selectivity of SAPO-37 catalysts at varioustemperatures Tem- perature Time Conversion Selectivity Yield System ° C.mins mol % mol % mol % SAPO-37(0.21) 130 30 33.7 97.1 32.7 SAPO-37(0.21)130 60 55.3 95.3 52.8 SAPO-37(0.21) 130 90 69.5 95.0 66.0 SAPO-37(0.21)130 120 78.1 96.1 75.1 SAPO-37(0.21) 130 150 84.6 95.5 80.8SAPO-37(0.21) 130 180 89.3 96.0 85.7 SAPO-37(0.21) 130 210 92.2 95.488.0 SAPO-37(0.21) 130 240 94.2 95.7 90.2 SAPO-37(0.21) 130 270 95.696.7 92.4 SAPO-37(0.21) 130 300 96.5 96.7 93.4 SAPO-37(0.21) 130 33097.8 96.1 94.0 SAPO-37(0.21) 130 360 98.2 94.6 92.9 SAPO-37(0.21) 130390 98.7 94.0 92.8 SAPO-37(0.21) 130 420 98.9 93.5 92.4 SAPO-37(0.21)AN130 30 30.2 100.0 30.2 SAPO-37(0.21)AN 130 60 54.1 99.1 53.6SAPO-37(0.21)AN 130 90 71.0 98.6 70.0 SAPO-37(0.21)AN 130 120 82.5 99.081.6 SAPO-37(0.21)AN 130 150 88.4 98.3 86.9 SAPO-37(0.21)AN 130 180 93.497.8 91.3 SAPO-37(0.21)AN 130 210 96.5 97.9 94.4 SAPO-37(0.21)AN 130 24097.9 97.8 95.7 SAPO-37(0.21)AN 130 270 98.4 98.1 96.5 SAPO-37(0.21)AN130 300 99.0 98.4 97.4 SAPO-37(0.21)AN 130 330 99.3 97.7 97.0SAPO-37(0.21)AN 130 360 99.5 97.8 97.3 SAPO-37(0.21)AN 130 390 99.7 97.997.6 SAPO-37(0.21)AN 130 420 99.8 97.8 97.6 SAPO-37(0.42) 130 30 33.596.4 32.3 SAPO-37(0.42) 130 60 53.0 98.4 52.1 SAPO-37(0.42) 130 90 69.094.9 65.5 SAPO-37(0.42) 130 120 78.3 95.7 74.9 SAPO-37(0.42) 130 15085.0 93.5 79.5 SAPO-37(0.42) 130 180 89.8 93.3 83.8 SAPO-37(0.42) 130210 92.3 92.7 85.5 SAPO-37(0.42) 130 240 94.3 91.3 86.1 SAPO-37(0.42)130 270 96.0 90.5 86.8 SAPO-37(0.42) 130 300 97.1 91.1 88.5SAPO-37(0.42) 130 330 97.6 90.7 88.5 SAPO-37(0.42) 130 360 98.1 91.089.2 SAPO-37(0.42) 130 390 98.5 90.7 89.3 SAPO-37(0.42) 130 420 98.890.3 89.1 SAPO-37(0.63) 130 30 38.2 91.6 35.0 SAPO-37(0.63) 130 60 58.491.5 53.4 SAPO-37(0.63) 130 90 73.1 90.3 66.1 SAPO-37(0.63) 130 120 80.890.4 73.0 SAPO-37(0.63) 130 150 87.0 90.9 79.1 SAPO-37(0.63) 130 18091.4 90.9 83.0 SAPO-37(0.63) 130 210 94.3 90.9 85.7 SAPO-37(0.63) 130240 96.5 89.3 86.2 SAPO-37(0.63) 130 270 97.8 89.3 87.3 SAPO-37(0.63)130 300 98.6 88.9 87.7 SAPO-37(0.63) 130 330 99.3 89.9 89.2SAPO-37(0.63) 130 360 99.5 88.1 87.7 SAPO-37(0.63) 130 390 99.7 88.888.5 SAPO-37(0.63) 130 420 99.8 88.4 88.2 SAPO-37(0.21) 150 15 44.5 94.542.1 SAPO-37(0.21) 150 30 75.4 95.7 72.1 SAPO-37(0.21) 150 45 87.3 94.782.7 SAPO-37(0.21) 150 60 95.0 92.8 88.2 SAPO-37(0.21) 150 75 97.2 92.589.9 SAPO-37(0.21) 150 90 98.7 93.7 92.4 SAPO-37(0.21) 150 105 99.4 92.792.2 SAPO-37(0.21) 150 120 99.7 91.1 90.8 SAPO-37(0.21) 150 135 99.892.5 92.3 SAPO-37(0.21) 150 150 99.9 92.7 92.6 SAPO-37(0.21) 150 16599.9 91.6 91.6 SAPO-37(0.21) 150 180 99.9 91.4 91.4 SAPO-37(0.21) 150195 100.0 91.3 91.3 SAPO-37(0.21) 150 210 100.0 91.3 91.3 SAPO-37(0.21)150 225 100.0 91.0 91.0 SAPO-37(0.21) 150 240 100.0 90.8 90.8SAPO-37(0.42) 150 15 44.6 94.6 42.2 SAPO-37(0.42) 150 30 69.8 90.2 62.9SAPO-37(0.42) 150 45 80.8 88.9 71.8 SAPO-37(0.42) 150 60 87.3 89.5 78.1SAPO-37(0.42) 150 75 93.2 90.4 84.2 SAPO-37(0.42) 150 90 95.2 91.1 86.7SAPO-37(0.42) 150 105 96.6 90.1 87.1 SAPO-37(0.42) 150 120 97.9 88.086.1 SAPO-37(0.42) 150 135 98.5 89.4 88.1 SAPO-37(0.42) 150 150 99.089.5 88.7 SAPO-37(0.42) 150 165 99.3 90.6 90.0 SAPO-37(0.42) 150 18099.5 90.9 90.5 SAPO-37(0.42) 150 195 99.7 91.1 90.8 SAPO-37(0.42) 150210 99.8 91.0 90.8 SAPO-37(0.42) 150 225 99.9 88.5 88.4 SAPO-37(0.42)150 240 99.9 88.7 88.7 SAPO-37(0.63) 150 15 45.5 84.3 38.3 SAPO-37(0.63)150 30 66.7 82.1 54.8 SAPO-37(0.63) 150 45 79.5 84.4 67.1 SAPO-37(0.63)150 60 86.7 83.3 72.2 SAPO-37(0.63) 150 75 90.4 84.1 76.0 SAPO-37(0.63)150 90 92.1 85.0 78.3 SAPO-37(0.63) 150 105 94.7 84.1 79.6 SAPO-37(0.63)150 120 96.2 84.2 81.0 SAPO-37(0.63) 150 135 97.2 84.2 81.8SAPO-37(0.63) 150 150 98.0 85.2 83.5 SAPO-37(0.63) 150 165 98.6 85.083.8 SAPO-37(0.63) 150 180 98.9 85.2 84.2 SAPO-37(0.63) 150 195 99.284.3 83.6 SAPO-37(0.63) 150 210 99.4 83.8 83.4 SAPO-37(0.63) 150 22599.6 83.7 83.3 SAPO-37(0.63) 150 240 99.7 84.1 83.8 SAPO-37(0.21) 170 527.2 97.1 26.4 SAPO-37(0.21) 170 10 57.9 92.7 53.7 SAPO-37(0.21) 170 1577.5 91.1 70.6 SAPO-37(0.21) 170 20 88.2 91.3 80.5 SAPO-37(0.21) 170 2593.9 91.2 85.6 SAPO-37(0.21) 170 30 96.3 90.3 87.0 SAPO-37(0.21) 170 3597.9 91.0 89.1 SAPO-37(0.21) 170 40 98.6 90.4 89.2 SAPO-37(0.21) 170 4599.1 89.7 88.9 SAPO-37(0.21) 170 50 99.5 91.1 90.6 SAPO-37(0.21) 170 5599.7 89.9 89.6 SAPO-37(0.21) 170 60 99.8 90.1 89.9 SAPO-37(0.42) 170 518.2 96.7 17.6 SAPO-37(0.42) 170 10 46.5 93.4 43.4 SAPO-37(0.42) 170 1563.5 94.3 59.9 SAPO-37(0.42) 170 20 75.0 94.9 71.2 SAPO-37(0.42) 170 2583.4 92.0 76.7 SAPO-37(0.42) 170 30 89.8 92.2 82.8 SAPO-37(0.42) 170 3593.2 90.2 84.1 SAPO-37(0.42) 170 40 95.5 88.8 84.8 SAPO-37(0.42) 170 4597.0 89.0 86.3 SAPO-37(0.42) 170 50 98.4 90.1 88.7 SAPO-37(0.42) 170 5598.8 89.3 88.2 SAPO-37(0.42) 170 60 98.9 89.9 88.9 SAPO-37(0.63) 170 527.8 79.2 22.0 SAPO-37(0.63) 170 10 50.9 82.9 42.2 SAPO-37(0.63) 170 1568.1 83.2 56.7 SAPO-37(0.63) 170 20 76.6 83.7 64.2 SAPO-37(0.63) 170 2583.3 84.9 70.7 SAPO-37(0.63) 170 30 88.5 82.7 73.2 SAPO-37(0.63) 170 3591.8 82.7 75.9 SAPO-37(0.63) 170 40 93.5 82.3 77.0 SAPO-37(0.63) 170 4594.9 82.9 78.7 SAPO-37(0.63) 170 50 96.1 82.5 79.3 SAPO-37(0.63) 170 5596.9 83.9 81.3 SAPO-37(0.63) 170 60 97.6 83.9 81.9 SAPO-37(0.21) 190 541.3 98.1 40.6 SAPO-37(0.21) 190 10 72.0 98.0 70.5 SAPO-37(0.21) 190 1586.3 96.1 82.9 SAPO-37(0.21) 190 20 92.9 92.4 85.9 SAPO-37(0.21) 190 2597.3 90.6 88.1 SAPO-37(0.21) 190 30 98.3 91.2 89.6 SAPO-37(0.21) 190 3599.1 91.7 90.9 SAPO-37(0.21) 190 40 99.5 91.1 90.6 SAPO-37(0.21) 190 4599.7 92.4 92.1 SAPO-37(0.21) 190 50 99.8 89.6 89.4 SAPO-37(0.21) 190 5599.9 88.7 88.6 SAPO-37(0.21) 190 60 99.9 89.8 89.7 SAPO-37(0.42) 190 529.5 100.0 29.5 SAPO-37(0.42) 190 10 66.4 100.0 66.4 SAPO-37(0.42) 19015 87.1 95.6 83.2 SAPO-37(0.42) 190 20 93.7 95.2 89.2 SAPO-37(0.42) 19025 97.0 96.3 93.4 SAPO-37(0.42) 190 30 98.6 96.0 94.6 SAPO-37(0.42) 19035 99.3 96.6 96.0 SAPO-37(0.42) 190 40 99.7 93.2 93.0 SAPO-37(0.42) 19045 99.8 93.3 93.1 SAPO-37(0.42) 190 50 99.9 91.8 91.8 SAPO-37(0.42) 19055 99.9 92.3 92.2 SAPO-37(0.42) 190 60 100.0 90.6 90.6 SAPO-37(0.63) 1905 35.9 85.5 30.7 SAPO-37(0.63) 190 10 70.8 84.3 59.6 SAPO-37(0.63) 19015 87.7 80.9 70.9 SAPO-37(0.63) 190 20 92.2 80.8 74.5 SAPO-37(0.63) 19025 95.8 80.0 76.7 SAPO-37(0.63) 190 30 97.1 81.2 78.8 SAPO-37(0.63) 19035 98.0 79.7 78.2 SAPO-37(0.63) 190 40 98.7 78.9 77.9 SAPO-37(0.63) 19045 99.0 78.4 77.6 SAPO-37(0.63) 190 50 99.3 79.2 78.7 SAPO-37(0.63) 19055 99.5 79.0 78.5 SAPO-37(0.63) 190 60 99.7 79.5 79.3

TABLE 13 Final conversion and selectivity of SAPO-37 catalysts atvarious temperatures ε- caprolactam Time Conversion selectivity Systemmins mol % mol % 130° C. SAPO-37(0.21) 420 98.9 93.5 SAPO-37(0.21) 42099.8 97.8 AN SAPO-37(0.42) 420 98.8 90.3 SAPO-37(0.63) 420 99.8 88.4150° C. SAPO-37(0.21) 240 100.0 90.8 SAPO-37(0.42) 240 99.9 88.7SAPO-37(0.63) 240 99.7 84.1 170° C. SAPO-37(0.21) 60 99.8 90.1SAPO-37(0.42) 60 98.9 89.9 SAPO-37(0.63) 60 97.6 83.9 190° C.SAPO-37(0.21) 60 99.9 89.8 SAPO-37(0.42) 60 100.0 85.4 SAPO-37(0.63) 6099.7 79.5

The results in Tables 12 and 13 indicate high levels of conversion andselectivity using SAPO-37 as the catalyst and benzonitrile as thesolvent in a liquid phase reaction. The data in Tables 12 and 13 showconversion greater than 97.5% within the measured times, whileselectivity for ε-caprolactam ranged from about 80% for SAPO-37(0.63) at190° C. to about 98% for SAPO-37(0.21) at 130° C. in anhydrousbenzonitrile.

Generally, the SAPO-37(0.21) provided higher selectivity than theSAPO-37(0.42), which in turn provided higher selectivity than theSAPO-37(0.63), although high selectivity and conversion were seen forail three catalysts. These results are consistent with the higherquantity of acid site suggested by the characterization data in Example2.

Liquid Beckmann Rearrangement of Cyclododecanone to ω-Laurolactam

The Beckmann rearrangement is also known to be useful in producingω-laurolactam from cyclododecanone (see FIG. 1B).

The same experimental procedure as for the liquid reactions withcyclohexanone oxime were performed with cyclododecanone oxime usingSAPO-37(0.21) and SAPO-11 catalysts. The reaction was performed at 130°C., with 175 mg of cyclododecanone oxime, 100 mg of catalyst, and 20 mlof benzonitrile. The gas chromatogram retention times were 8.4 minutesfor cyclododecanone, 10.8 minutes for cyclododecanone oxime, and 11.8minutes for ω-laurolactam. The results using SAPO-37(0.21) are providedin FIG. 19 and Table 14. The results using SAPO-11 are provided in FIG.20.

TABLE 14 Results of liquid cyclododecanone oxime reaction SAPO-37(0.21),190° C. Time/minutes Conversion/mol % Selectivity/mol % Yield/mol % 583.9 99.9 83.9 10 99.3 99.4 98.8 60 100.0 99.8 99.8

FIG. 21 illustrates very high conversion and selectivity using SAPO-37as the catalyst, while FIG. 22 illustrates much lower conversion andselectivity using SAPO-37 as the catalyst. The only notably by-productfound using SAPO-37 was cyclododecanone.

While the present disclosure is primarily directed to production ofε-caprolactam and ω-laurolactam, it should be understood that thefeatures disclosed herein have application to the production of otherlactams and other monomers.

While this invention has been described as relative to exemplarydesigns, the present invention may be further modified within the spiritand scope of this disclosure. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains.

What is claimed is:
 1. A catalyst comprising: a silicon-containingaluminophosphate framework with the IZA framework code FAU; and aplurality of discrete Brønsted acid sites positioned in an interior ofthe framework, the acid sites comprising silicon isomorphouslysubstituted for phosphorous in the framework; wherein the catalyst is aSAPO-37 type catalyst, and the catalyst is formed from a gel having amolar ratio of silicon to phosphorous from 0.21:1 to 0.42:1.
 2. Thecatalyst of claim 1, wherein the silicon comprises about 1 wt. % toabout 10 wt. % of the total weight of the catalyst.
 3. The catalyst ofclaim 2, wherein the silicon comprises about 2 wt. % to about 9.1 wt. %of the total weight of the catalyst.
 4. A silicoaluminophosphatecatalyst having a microporous crystalline framework structure having acomposition on an anhydrous basis of:mR:(Si_(x)Al_(y)P_(z))O₂ wherein: R is at least one organic templatingagent; m is from 0.02 to 0.3; and x, y, and z, are selected within thevalues bounded by the points A, B, C, D, and E on a ternary diagram,where: x y z A 0.01 0.47 0.52 B 0.94 0.01 0.05 C 0.98 0.01 0.01 C 0.390.60 0.01 E 0.01 0.60 0.39

the catalyst comprising a plurality of discrete Brønsted acid sitespositioned in an interior of the framework, the acid sites comprisingsilicon isomorphously substituted for phosphorous in the framework;wherein the ratio of silicon to phosphorous is from 0.21:1 to 0.42:1. 5.The catalyst of claim 4, wherein x, y, and z, are selected within thevalues bounded by the points a, b, c, d, and e on a ternary diagram,where: x y z a 0.02 0.49 0.49 b 0.25 0.37 0.38 c 0.25 0.48 0.27 d 0.130.60 0.27 e 0.02 0.60  0.38.


6. The catalyst of claim 5, wherein the catalyst is a SAPO-37 catalyst.7. The catalyst of claim 4, wherein the catalyst is a silicon-containingaluminophosphate framework with the IZA framework code FAU.
 8. Thecatalyst of claim 4, wherein the at least one organic templating agentis at least one of tetrmethylammonium hydroxide pentahydrate andtetrapropylammonium hydroxide.
 9. The catalyst of claim 4, wherein thesilicon comprises about 1 wt. % to about 10 wt. % of the total weight ofthe catalyst.
 10. A method of forming a SAPO-37 catalyst, comprising:adding an aluminum source to a phosphorous source to form analuminum/phosphorous mixture; dissolving tetrmethylammonium hydroxidepentahydrate in tetrapropylammonium hydroxide to form a TMAOH/TPAOHsolution; adding fumed silica to the TMAOH/TPAOH solution to form astructural template solution; adding the structural template solution tothe aluminum/phosphorous mixture to form a gel having a ratio of siliconto phosphorous from 0.21:1 to about 0.42:1; and heating the gel to formthe catalyst, the catalyst having a silicon-containing aluminophosphateframework with the IZA framework code FAU and a plurality of discreteBrønsted acid sites positioned in an interior of the framework, the acidsites comprising silicon isomorphously substituted for phosphorous inthe framework.
 11. The method of claim 5, wherein the aluminum source isaluminum oxide and the phosphorous source is phosphoric acid.
 12. Themethod of claim 5, further comprising: isolating a product by at leastone of centrifuging, filtering, or washing the catalyst; and drying theisolated catalyst.